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	$137.63	11.478%	$153.4272	$153.43	$153.45	$153.40
Purchase #2	$54.96	12.651%	$61.913	$61.91	$61.90	$61.90
Purchase #3	$205.51	3.505%	$212.7131	$212.71	$212.70	$212.70
Purchase #4	$236.70	7.498%	$254.4478	$254.45	$254.45	$254.40
Purchase #5	$167.74	7.673%	$180.6107	$180.61	$180.60	$180.60
Purchase #6	$143.25	9.122%	$156.3173	$156.32	$156.30	$156.30
Purchase #7	$120.97	13.165%	$136.8957	$136.90	$136.90	$136.90
7 purchase totals =	$1,066.76		$1,156.3248	$1,156.33	$1,156.30	$1,156.20