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	$133.70	7.782%	$144.1045	$144.10	$144.10	$144.10
Purchase #2	$245.55	3.553%	$254.2744	$254.27	$254.25	$254.30
Purchase #3	$182.47	12.821%	$205.8645	$205.86	$205.85	$205.90
Purchase #4	$151.60	12.545%	$170.6182	$170.62	$170.60	$170.60
Purchase #5	$109.90	13.214%	$124.4222	$124.42	$124.40	$124.40
Purchase #6	$37.31	5.274%	$39.2777	$39.28	$39.30	$39.30
Purchase #7	$70.76	11.304%	$78.7587	$78.76	$78.75	$78.80
7 purchase totals =	$931.29		$1,017.3202	$1,017.31	$1,017.25	$1,017.40