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	$206.32	4.336%	$215.266	$215.27	$215.25	$215.30
Purchase #2	$180.36	5.794%	$190.8101	$190.81	$190.80	$190.80
Purchase #3	$204.25	12.688%	$230.1652	$230.17	$230.15	$230.20
Purchase #4	$82.91	6.796%	$88.5446	$88.54	$88.55	$88.50
Purchase #5	$140.99	4.114%	$146.7903	$146.79	$146.80	$146.80
Purchase #6	$229.73	5.409%	$242.1561	$242.16	$242.15	$242.20
Purchase #7	$57.88	3.456%	$59.8803	$59.88	$59.90	$59.90
7 purchase totals =	$1,102.44		$1,173.6126	$1,173.62	$1,173.60	$1,173.70