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	$174.66	12.668%	$196.7859	$196.79	$196.80	$196.80
Purchase #2	$172.55	5.265%	$181.6348	$181.63	$181.65	$181.60
Purchase #3	$192.54	12.656%	$216.9079	$216.91	$216.90	$216.90
Purchase #4	$56.27	10.725%	$62.305	$62.31	$62.30	$62.30
Purchase #5	$198.73	6.230%	$211.1109	$211.11	$211.10	$211.10
Purchase #6	$168.25	6.802%	$179.6944	$179.69	$179.70	$179.70
Purchase #7	$249.87	13.482%	$283.5575	$283.56	$283.55	$283.60
7 purchase totals =	$1,212.87		$1,331.9964	$1,332.00	$1,332.00	$1,332.00