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	$106.80	11.737%	$119.3351	$119.34	$119.35	$119.30
Purchase #2	$121.82	4.347%	$127.1155	$127.12	$127.10	$127.10
Purchase #3	$64.80	9.419%	$70.9035	$70.90	$70.90	$70.90
Purchase #4	$72.59	5.592%	$76.6492	$76.65	$76.65	$76.60
Purchase #5	$104.61	4.836%	$109.6689	$109.67	$109.65	$109.70
Purchase #6	$245.53	9.783%	$269.5502	$269.55	$269.55	$269.60
Purchase #7	$109.62	10.333%	$120.947	$120.95	$120.95	$120.90
7 purchase totals =	$825.77		$894.1694	$894.18	$894.15	$894.10