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	$131.40	8.204%	$142.1801	$142.18	$142.20	$142.20
Purchase #2	$211.30	10.602%	$233.702	$233.70	$233.70	$233.70
Purchase #3	$209.52	3.326%	$216.4886	$216.49	$216.50	$216.50
Purchase #4	$80.78	6.108%	$85.714	$85.71	$85.70	$85.70
Purchase #5	$219.50	8.462%	$238.0741	$238.07	$238.05	$238.10
Purchase #6	$9.48	9.613%	$10.3913	$10.39	$10.40	$10.40
Purchase #7	$160.59	3.246%	$165.8028	$165.80	$165.80	$165.80
7 purchase totals =	$1,022.57		$1,092.3529	$1,092.34	$1,092.35	$1,092.40