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	$59.59	4.740%	$62.4146	$62.41	$62.40	$62.40
Purchase #2	$224.58	11.711%	$250.8806	$250.88	$250.90	$250.90
Purchase #3	$118.52	7.752%	$127.7077	$127.71	$127.70	$127.70
Purchase #4	$146.29	3.300%	$151.1176	$151.12	$151.10	$151.10
Purchase #5	$165.86	7.387%	$178.1121	$178.11	$178.10	$178.10
Purchase #6	$30.37	3.714%	$31.4979	$31.50	$31.50	$31.50
Purchase #7	$170.51	12.664%	$192.1034	$192.10	$192.10	$192.10
7 purchase totals =	$915.72		$993.8339	$993.83	$993.80	$993.80