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	$170.37	13.817%	$193.91	$193.91	$193.90	$193.90
Purchase #2	$83.37	3.608%	$86.378	$86.38	$86.40	$86.40
Purchase #3	$33.56	5.561%	$35.4263	$35.43	$35.45	$35.40
Purchase #4	$59.41	9.739%	$65.1959	$65.20	$65.20	$65.20
Purchase #5	$185.55	13.821%	$211.1949	$211.19	$211.20	$211.20
Purchase #6	$218.81	6.630%	$233.3171	$233.32	$233.30	$233.30
Purchase #7	$231.54	11.838%	$258.9497	$258.95	$258.95	$258.90
7 purchase totals =	$982.61		$1,084.3719	$1,084.38	$1,084.40	$1,084.30