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	$142.37	3.347%	$147.1351	$147.14	$147.15	$147.10
Purchase #2	$196.99	6.170%	$209.1443	$209.14	$209.15	$209.10
Purchase #3	$83.88	11.520%	$93.543	$93.54	$93.55	$93.50
Purchase #4	$31.81	12.824%	$35.8893	$35.89	$35.90	$35.90
Purchase #5	$124.44	5.187%	$130.8947	$130.89	$130.90	$130.90
Purchase #6	$156.30	5.144%	$164.3401	$164.34	$164.35	$164.30
Purchase #7	$190.83	10.818%	$211.474	$211.47	$211.45	$211.50
7 purchase totals =	$926.62		$992.4205	$992.41	$992.45	$992.30