Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$153.89	11.183%	$171.0995	$171.10	$171.10	$171.10
Purchase #2	$211.49	13.620%	$240.2949	$240.29	$240.30	$240.30
Purchase #3	$207.56	8.227%	$224.636	$224.64	$224.65	$224.60
Purchase #4	$185.83	5.749%	$196.5134	$196.51	$196.50	$196.50
Purchase #5	$103.34	13.279%	$117.0625	$117.06	$117.05	$117.10
Purchase #6	$178.74	7.258%	$191.7129	$191.71	$191.70	$191.70
Purchase #7	$111.83	10.542%	$123.6191	$123.62	$123.60	$123.60
7 purchase totals =	$1,152.68		$1,264.9383	$1,264.93	$1,264.90	$1,264.90