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	$239.73	11.564%	$267.4524	$267.45	$267.45	$267.50
Purchase #2	$67.65	11.413%	$75.3709	$75.37	$75.35	$75.40
Purchase #3	$58.67	6.144%	$62.2747	$62.27	$62.25	$62.30
Purchase #4	$131.37	13.764%	$149.4518	$149.45	$149.45	$149.50
Purchase #5	$222.80	11.231%	$247.8227	$247.82	$247.80	$247.80
Purchase #6	$196.57	11.380%	$218.9397	$218.94	$218.95	$218.90
Purchase #7	$98.85	12.398%	$111.1054	$111.11	$111.10	$111.10
7 purchase totals =	$1,015.64		$1,132.4176	$1,132.41	$1,132.35	$1,132.50