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	$231.31	6.251%	$245.7692	$245.77	$245.75	$245.80
Purchase #2	$51.60	6.404%	$54.9045	$54.90	$54.90	$54.90
Purchase #3	$219.41	9.648%	$240.5787	$240.58	$240.60	$240.60
Purchase #4	$166.73	11.156%	$185.3304	$185.33	$185.35	$185.30
Purchase #5	$99.67	5.571%	$105.2226	$105.22	$105.20	$105.20
Purchase #6	$113.92	5.132%	$119.7664	$119.77	$119.75	$119.80
Purchase #7	$239.53	3.869%	$248.7974	$248.80	$248.80	$248.80
7 purchase totals =	$1,122.17		$1,200.3692	$1,200.37	$1,200.35	$1,200.40