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	$91.28	5.730%	$96.5103	$96.51	$96.50	$96.50
Purchase #2	$86.63	3.314%	$89.5009	$89.50	$89.50	$89.50
Purchase #3	$132.25	4.450%	$138.1351	$138.14	$138.15	$138.10
Purchase #4	$148.69	8.214%	$160.9034	$160.90	$160.90	$160.90
Purchase #5	$184.59	7.213%	$197.9045	$197.90	$197.90	$197.90
Purchase #6	$58.29	12.224%	$65.4154	$65.42	$65.40	$65.40
Purchase #7	$241.52	9.218%	$263.7833	$263.78	$263.80	$263.80
7 purchase totals =	$943.25		$1,012.1529	$1,012.15	$1,012.15	$1,012.10