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	$169.69	7.355%	$182.1707	$182.17	$182.15	$182.20
Purchase #2	$72.98	13.480%	$82.8177	$82.82	$82.80	$82.80
Purchase #3	$207.82	7.729%	$223.8824	$223.88	$223.90	$223.90
Purchase #4	$137.60	10.873%	$152.5612	$152.56	$152.55	$152.60
Purchase #5	$131.62	13.446%	$149.3176	$149.32	$149.30	$149.30
Purchase #6	$154.98	7.590%	$166.743	$166.74	$166.75	$166.70
Purchase #7	$204.36	9.473%	$223.719	$223.72	$223.70	$223.70
7 purchase totals =	$1,079.05		$1,181.2116	$1,181.21	$1,181.15	$1,181.20