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	$79.60	6.226%	$84.5559	$84.56	$84.55	$84.60
Purchase #2	$245.70	3.617%	$254.587	$254.59	$254.60	$254.60
Purchase #3	$203.96	6.103%	$216.4077	$216.41	$216.40	$216.40
Purchase #4	$56.31	9.157%	$61.4663	$61.47	$61.45	$61.50
Purchase #5	$212.86	10.467%	$235.1401	$235.14	$235.15	$235.10
Purchase #6	$175.77	11.871%	$196.6357	$196.64	$196.65	$196.60
Purchase #7	$60.98	3.162%	$62.9082	$62.91	$62.90	$62.90
7 purchase totals =	$1,035.18		$1,111.7009	$1,111.72	$1,111.70	$1,111.70