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	$191.85	4.376%	$200.2454	$200.25	$200.25	$200.20
Purchase #2	$244.71	12.106%	$274.3346	$274.33	$274.35	$274.30
Purchase #3	$222.87	13.548%	$253.0644	$253.06	$253.05	$253.10
Purchase #4	$64.27	3.337%	$66.4147	$66.41	$66.40	$66.40
Purchase #5	$109.72	5.645%	$115.9137	$115.91	$115.90	$115.90
Purchase #6	$190.41	10.438%	$210.285	$210.29	$210.30	$210.30
Purchase #7	$184.74	13.818%	$210.2674	$210.27	$210.25	$210.30
7 purchase totals =	$1,208.57		$1,330.5252	$1,330.52	$1,330.50	$1,330.50