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	$184.75	8.432%	$200.3281	$200.33	$200.35	$200.30
Purchase #2	$33.52	6.644%	$35.7471	$35.75	$35.75	$35.70
Purchase #3	$50.61	12.835%	$57.1058	$57.11	$57.10	$57.10
Purchase #4	$147.76	4.498%	$154.4062	$154.41	$154.40	$154.40
Purchase #5	$77.98	6.839%	$83.3131	$83.31	$83.30	$83.30
Purchase #6	$178.50	10.326%	$196.9319	$196.93	$196.95	$196.90
Purchase #7	$46.46	10.215%	$51.2059	$51.21	$51.20	$51.20
7 purchase totals =	$719.58		$779.0381	$779.05	$779.05	$778.90