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	$222.43	5.354%	$234.3389	$234.34	$234.35	$234.30
Purchase #2	$35.53	4.432%	$37.1047	$37.10	$37.10	$37.10
Purchase #3	$100.97	12.167%	$113.255	$113.26	$113.25	$113.30
Purchase #4	$233.61	3.769%	$242.4148	$242.41	$242.40	$242.40
Purchase #5	$137.83	7.308%	$147.9026	$147.90	$147.90	$147.90
Purchase #6	$35.52	10.738%	$39.3341	$39.33	$39.35	$39.30
Purchase #7	$180.56	5.132%	$189.8263	$189.83	$189.85	$189.80
7 purchase totals =	$946.45		$1,004.1764	$1,004.17	$1,004.20	$1,004.10