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	$210.70	6.836%	$225.1035	$225.10	$225.10	$225.10
Purchase #2	$75.76	4.810%	$79.4041	$79.40	$79.40	$79.40
Purchase #3	$165.28	4.236%	$172.2813	$172.28	$172.30	$172.30
Purchase #4	$249.84	4.833%	$261.9148	$261.91	$261.90	$261.90
Purchase #5	$126.94	13.801%	$144.459	$144.46	$144.45	$144.50
Purchase #6	$122.82	3.813%	$127.5031	$127.50	$127.50	$127.50
Purchase #7	$142.98	12.404%	$160.7152	$160.72	$160.70	$160.70
7 purchase totals =	$1,094.32		$1,171.3810	$1,171.37	$1,171.35	$1,171.40