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	$94.64	12.123%	$106.1132	$106.11	$106.10	$106.10
Purchase #2	$61.41	3.180%	$63.3628	$63.36	$63.35	$63.40
Purchase #3	$83.94	6.438%	$89.3441	$89.34	$89.35	$89.30
Purchase #4	$144.78	4.526%	$151.3327	$151.33	$151.35	$151.30
Purchase #5	$192.94	9.658%	$211.5741	$211.57	$211.55	$211.60
Purchase #6	$226.89	8.406%	$245.9624	$245.96	$245.95	$246.00
Purchase #7	$60.44	11.492%	$67.3858	$67.39	$67.40	$67.40
7 purchase totals =	$865.04		$935.0751	$935.06	$935.05	$935.10