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	$158.61	3.739%	$164.5404	$164.54	$164.55	$164.50
Purchase #2	$96.95	13.132%	$109.6815	$109.68	$109.70	$109.70
Purchase #3	$221.94	5.506%	$234.16	$234.16	$234.15	$234.20
Purchase #4	$43.26	11.199%	$48.1047	$48.10	$48.10	$48.10
Purchase #5	$79.83	12.524%	$89.8279	$89.83	$89.85	$89.80
Purchase #6	$239.32	6.854%	$255.723	$255.72	$255.70	$255.70
Purchase #7	$123.45	13.192%	$139.7355	$139.74	$139.75	$139.70
7 purchase totals =	$963.36		$1,041.7730	$1,041.77	$1,041.80	$1,041.70