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	$227.31	4.815%	$238.255	$238.26	$238.25	$238.30
Purchase #2	$78.73	13.445%	$89.3152	$89.32	$89.30	$89.30
Purchase #3	$169.95	7.321%	$182.392	$182.39	$182.40	$182.40
Purchase #4	$41.98	4.342%	$43.8028	$43.80	$43.80	$43.80
Purchase #5	$147.91	8.624%	$160.6658	$160.67	$160.65	$160.70
Purchase #6	$183.25	7.284%	$196.5979	$196.60	$196.60	$196.60
Purchase #7	$186.77	13.524%	$212.0288	$212.03	$212.05	$212.00
7 purchase totals =	$1,035.90		$1,123.0575	$1,123.07	$1,123.05	$1,123.10