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	$222.94	8.213%	$241.2501	$241.25	$241.25	$241.30
Purchase #2	$152.75	12.512%	$171.8621	$171.86	$171.85	$171.90
Purchase #3	$107.94	6.111%	$114.5362	$114.54	$114.55	$114.50
Purchase #4	$135.33	11.560%	$150.9741	$150.97	$150.95	$151.00
Purchase #5	$232.56	7.675%	$250.409	$250.41	$250.40	$250.40
Purchase #6	$44.26	5.605%	$46.7408	$46.74	$46.75	$46.70
Purchase #7	$170.60	3.467%	$176.5147	$176.51	$176.50	$176.50
7 purchase totals =	$1,066.38		$1,152.2870	$1,152.28	$1,152.25	$1,152.30