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	$147.72	11.318%	$164.4389	$164.44	$164.45	$164.40
Purchase #2	$217.50	11.282%	$242.0384	$242.04	$242.05	$242.00
Purchase #3	$203.42	3.213%	$209.9559	$209.96	$209.95	$210.00
Purchase #4	$85.56	11.443%	$95.3506	$95.35	$95.35	$95.40
Purchase #5	$54.82	5.839%	$58.0209	$58.02	$58.00	$58.00
Purchase #6	$103.93	3.112%	$107.1643	$107.16	$107.15	$107.20
Purchase #7	$111.95	12.470%	$125.9102	$125.91	$125.90	$125.90
7 purchase totals =	$924.90		$1,002.8792	$1,002.88	$1,002.85	$1,002.90