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	$149.57	4.351%	$156.0778	$156.08	$156.10	$156.10
Purchase #2	$77.53	7.330%	$83.2129	$83.21	$83.20	$83.20
Purchase #3	$85.70	4.408%	$89.4777	$89.48	$89.50	$89.50
Purchase #4	$216.61	13.591%	$246.0495	$246.05	$246.05	$246.00
Purchase #5	$168.74	7.445%	$181.3027	$181.30	$181.30	$181.30
Purchase #6	$116.76	11.855%	$130.6019	$130.60	$130.60	$130.60
Purchase #7	$150.63	11.459%	$167.8907	$167.89	$167.90	$167.90
7 purchase totals =	$965.54		$1,054.6132	$1,054.61	$1,054.65	$1,054.60