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	$173.79	13.285%	$196.878	$196.88	$196.90	$196.90
Purchase #2	$54.88	11.157%	$61.003	$61.00	$61.00	$61.00
Purchase #3	$29.28	3.423%	$30.2823	$30.28	$30.30	$30.30
Purchase #4	$99.26	4.523%	$103.7495	$103.75	$103.75	$103.70
Purchase #5	$229.61	3.566%	$237.7979	$237.80	$237.80	$237.80
Purchase #6	$171.49	10.157%	$188.9082	$188.91	$188.90	$188.90
Purchase #7	$52.58	11.326%	$58.5352	$58.54	$58.55	$58.50
7 purchase totals =	$810.89		$877.1541	$877.16	$877.20	$877.10