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	$229.67	13.260%	$260.1242	$260.12	$260.10	$260.10
Purchase #2	$102.32	8.870%	$111.3958	$111.40	$111.40	$111.40
Purchase #3	$70.67	4.578%	$73.9053	$73.91	$73.90	$73.90
Purchase #4	$188.32	8.341%	$204.0278	$204.03	$204.05	$204.00
Purchase #5	$161.45	4.251%	$168.3132	$168.31	$168.30	$168.30
Purchase #6	$62.91	7.295%	$67.4993	$67.50	$67.50	$67.50
Purchase #7	$42.42	9.730%	$46.5475	$46.55	$46.55	$46.50
7 purchase totals =	$857.76		$931.8131	$931.82	$931.80	$931.70