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	$173.60	6.695%	$185.2225	$185.22	$185.20	$185.20
Purchase #2	$229.76	11.468%	$256.1089	$256.11	$256.10	$256.10
Purchase #3	$154.57	7.315%	$165.8768	$165.88	$165.90	$165.90
Purchase #4	$153.60	5.838%	$162.5672	$162.57	$162.55	$162.60
Purchase #5	$115.29	10.385%	$127.2629	$127.26	$127.25	$127.30
Purchase #6	$185.38	12.488%	$208.5303	$208.53	$208.55	$208.50
Purchase #7	$73.65	9.253%	$80.4648	$80.46	$80.45	$80.50
7 purchase totals =	$1,085.85		$1,186.0334	$1,186.03	$1,186.00	$1,186.10