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	$188.74	11.811%	$211.0321	$211.03	$211.05	$211.00
Purchase #2	$104.55	9.823%	$114.8199	$114.82	$114.80	$114.80
Purchase #3	$49.67	7.384%	$53.3376	$53.34	$53.35	$53.30
Purchase #4	$25.88	8.452%	$28.0674	$28.07	$28.05	$28.10
Purchase #5	$221.84	5.287%	$233.5687	$233.57	$233.55	$233.60
Purchase #6	$31.50	3.870%	$32.7191	$32.72	$32.70	$32.70
Purchase #7	$163.28	5.377%	$172.0596	$172.06	$172.05	$172.10
7 purchase totals =	$785.46		$845.6044	$845.61	$845.55	$845.60