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	$190.73	11.710%	$213.0645	$213.06	$213.05	$213.10
Purchase #2	$168.96	12.521%	$190.1155	$190.12	$190.10	$190.10
Purchase #3	$167.94	6.785%	$179.3347	$179.33	$179.35	$179.30
Purchase #4	$186.41	7.616%	$200.607	$200.61	$200.60	$200.60
Purchase #5	$145.48	4.360%	$151.8229	$151.82	$151.80	$151.80
Purchase #6	$250.50	13.465%	$284.2298	$284.23	$284.25	$284.20
Purchase #7	$75.71	9.546%	$82.9373	$82.94	$82.95	$82.90
7 purchase totals =	$1,185.73		$1,302.1117	$1,302.11	$1,302.10	$1,302.00