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	$152.70	7.483%	$164.1265	$164.13	$164.15	$164.10
Purchase #2	$240.86	10.371%	$265.8396	$265.84	$265.85	$265.80
Purchase #3	$29.80	13.656%	$33.8695	$33.87	$33.85	$33.90
Purchase #4	$146.82	7.681%	$158.0972	$158.10	$158.10	$158.10
Purchase #5	$64.84	10.241%	$71.4803	$71.48	$71.50	$71.50
Purchase #6	$236.29	13.159%	$267.3834	$267.38	$267.40	$267.40
Purchase #7	$84.98	13.335%	$96.3121	$96.31	$96.30	$96.30
7 purchase totals =	$956.29		$1,057.1086	$1,057.11	$1,057.15	$1,057.10