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	$75.41	13.429%	$85.5368	$85.54	$85.55	$85.50
Purchase #2	$83.75	9.382%	$91.6074	$91.61	$91.60	$91.60
Purchase #3	$173.63	7.481%	$186.6193	$186.62	$186.60	$186.60
Purchase #4	$194.43	13.459%	$220.5983	$220.60	$220.60	$220.60
Purchase #5	$200.59	11.275%	$223.2065	$223.21	$223.20	$223.20
Purchase #6	$174.44	9.553%	$191.1043	$191.10	$191.10	$191.10
Purchase #7	$94.60	5.342%	$99.6535	$99.65	$99.65	$99.70
7 purchase totals =	$996.85		$1,098.3261	$1,098.33	$1,098.30	$1,098.30