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	$247.79	4.141%	$258.051	$258.05	$258.05	$258.10
Purchase #2	$36.47	3.709%	$37.8227	$37.82	$37.80	$37.80
Purchase #3	$241.89	3.198%	$249.6256	$249.63	$249.65	$249.60
Purchase #4	$172.91	13.414%	$196.1041	$196.10	$196.10	$196.10
Purchase #5	$222.33	6.721%	$237.2728	$237.27	$237.25	$237.30
Purchase #6	$190.75	3.633%	$197.6799	$197.68	$197.70	$197.70
Purchase #7	$58.88	4.132%	$61.3129	$61.31	$61.30	$61.30
7 purchase totals =	$1,171.02		$1,237.8690	$1,237.86	$1,237.85	$1,237.90