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	$223.25	7.659%	$240.3487	$240.35	$240.35	$240.30
Purchase #2	$7.44	4.301%	$7.76	$7.76	$7.75	$7.80
Purchase #3	$245.31	7.734%	$264.2823	$264.28	$264.30	$264.30
Purchase #4	$42.89	5.384%	$45.1992	$45.20	$45.20	$45.20
Purchase #5	$72.48	3.288%	$74.8631	$74.86	$74.85	$74.90
Purchase #6	$150.49	12.760%	$169.6925	$169.69	$169.70	$169.70
Purchase #7	$244.75	12.207%	$274.6266	$274.63	$274.65	$274.60
7 purchase totals =	$986.61		$1,076.7724	$1,076.77	$1,076.80	$1,076.80