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	$196.57	13.799%	$223.6947	$223.69	$223.70	$223.70
Purchase #2	$63.76	11.800%	$71.2837	$71.28	$71.30	$71.30
Purchase #3	$224.57	4.447%	$234.5566	$234.56	$234.55	$234.60
Purchase #4	$228.73	11.622%	$255.313	$255.31	$255.30	$255.30
Purchase #5	$38.50	11.791%	$43.0395	$43.04	$43.05	$43.00
Purchase #6	$236.34	11.400%	$263.2828	$263.28	$263.30	$263.30
Purchase #7	$90.25	10.668%	$99.8779	$99.88	$99.90	$99.90
7 purchase totals =	$1,078.72		$1,191.0482	$1,191.04	$1,191.10	$1,191.10