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	$159.89	3.336%	$165.2239	$165.22	$165.20	$165.20
Purchase #2	$53.25	3.519%	$55.1239	$55.12	$55.10	$55.10
Purchase #3	$134.91	7.837%	$145.4829	$145.48	$145.50	$145.50
Purchase #4	$248.25	12.132%	$278.3677	$278.37	$278.35	$278.40
Purchase #5	$146.47	10.727%	$162.1818	$162.18	$162.20	$162.20
Purchase #6	$167.85	8.263%	$181.7194	$181.72	$181.70	$181.70
Purchase #7	$193.80	7.473%	$208.2827	$208.28	$208.30	$208.30
7 purchase totals =	$1,104.42		$1,196.3823	$1,196.37	$1,196.35	$1,196.40