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	$152.56	3.486%	$157.8782	$157.88	$157.90	$157.90
Purchase #2	$61.64	5.702%	$65.1547	$65.15	$65.15	$65.20
Purchase #3	$223.59	5.681%	$236.2921	$236.29	$236.30	$236.30
Purchase #4	$51.37	4.786%	$53.8286	$53.83	$53.85	$53.80
Purchase #5	$218.61	13.133%	$247.3201	$247.32	$247.30	$247.30
Purchase #6	$201.81	13.510%	$229.0745	$229.07	$229.05	$229.10
Purchase #7	$96.46	3.138%	$99.4869	$99.49	$99.50	$99.50
7 purchase totals =	$1,006.04		$1,089.0351	$1,089.03	$1,089.05	$1,089.10