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	$89.89	4.710%	$94.1238	$94.12	$94.10	$94.10
Purchase #2	$163.30	10.590%	$180.5935	$180.59	$180.60	$180.60
Purchase #3	$182.42	6.202%	$193.7337	$193.73	$193.75	$193.70
Purchase #4	$216.57	12.449%	$243.5308	$243.53	$243.55	$243.50
Purchase #5	$134.97	9.517%	$147.8151	$147.82	$147.80	$147.80
Purchase #6	$78.63	6.654%	$83.862	$83.86	$83.85	$83.90
Purchase #7	$80.48	11.399%	$89.6539	$89.65	$89.65	$89.70
7 purchase totals =	$946.26		$1,033.3128	$1,033.30	$1,033.30	$1,033.30