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	$201.65	4.744%	$211.2163	$211.22	$211.20	$211.20
Purchase #2	$155.93	9.438%	$170.6467	$170.65	$170.65	$170.60
Purchase #3	$66.68	7.853%	$71.9164	$71.92	$71.90	$71.90
Purchase #4	$33.83	11.742%	$37.8023	$37.80	$37.80	$37.80
Purchase #5	$104.33	5.282%	$109.8407	$109.84	$109.85	$109.80
Purchase #6	$53.85	9.768%	$59.1101	$59.11	$59.10	$59.10
Purchase #7	$245.43	7.165%	$263.0151	$263.02	$263.00	$263.00
7 purchase totals =	$861.70		$923.5476	$923.56	$923.50	$923.40