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	$94.55	4.520%	$98.8237	$98.82	$98.80	$98.80
Purchase #2	$81.81	13.760%	$93.0671	$93.07	$93.05	$93.10
Purchase #3	$72.75	7.740%	$78.3809	$78.38	$78.40	$78.40
Purchase #4	$81.98	9.349%	$89.6443	$89.64	$89.65	$89.60
Purchase #5	$128.92	3.268%	$133.1331	$133.13	$133.15	$133.10
Purchase #6	$157.31	6.592%	$167.6799	$167.68	$167.70	$167.70
Purchase #7	$30.60	9.824%	$33.6061	$33.61	$33.60	$33.60
7 purchase totals =	$647.92		$694.3351	$694.33	$694.35	$694.30