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	$125.61	12.281%	$141.0362	$141.04	$141.05	$141.00
Purchase #2	$180.69	10.260%	$199.2288	$199.23	$199.25	$199.20
Purchase #3	$195.71	5.643%	$206.7539	$206.75	$206.75	$206.80
Purchase #4	$40.30	6.817%	$43.0473	$43.05	$43.05	$43.00
Purchase #5	$191.27	11.825%	$213.8877	$213.89	$213.90	$213.90
Purchase #6	$156.71	6.210%	$166.4417	$166.44	$166.45	$166.40
Purchase #7	$83.49	3.179%	$86.1441	$86.14	$86.15	$86.10
7 purchase totals =	$973.78		$1,056.5397	$1,056.54	$1,056.60	$1,056.40