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	$213.62	11.331%	$237.8253	$237.83	$237.85	$237.80
Purchase #2	$184.60	6.259%	$196.1541	$196.15	$196.15	$196.20
Purchase #3	$245.76	11.405%	$273.7889	$273.79	$273.80	$273.80
Purchase #4	$40.98	10.274%	$45.1903	$45.19	$45.20	$45.20
Purchase #5	$101.59	10.121%	$111.8719	$111.87	$111.85	$111.90
Purchase #6	$68.59	6.567%	$73.0943	$73.09	$73.10	$73.10
Purchase #7	$149.58	6.538%	$159.3595	$159.36	$159.35	$159.40
7 purchase totals =	$1,004.72		$1,097.2843	$1,097.28	$1,097.30	$1,097.40