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	$188.41	12.417%	$211.8049	$211.80	$211.80	$211.80
Purchase #2	$48.52	10.128%	$53.4341	$53.43	$53.45	$53.40
Purchase #3	$128.36	7.415%	$137.8779	$137.88	$137.90	$137.90
Purchase #4	$169.75	13.762%	$193.111	$193.11	$193.10	$193.10
Purchase #5	$162.98	13.577%	$185.1078	$185.11	$185.10	$185.10
Purchase #6	$115.53	13.480%	$131.1034	$131.10	$131.10	$131.10
Purchase #7	$88.37	9.532%	$96.7934	$96.79	$96.80	$96.80
7 purchase totals =	$901.92		$1,009.2325	$1,009.22	$1,009.25	$1,009.20