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	$240.64	5.220%	$253.2014	$253.20	$253.20	$253.20
Purchase #2	$190.44	5.228%	$200.3962	$200.40	$200.40	$200.40
Purchase #3	$89.79	11.286%	$99.9237	$99.92	$99.90	$99.90
Purchase #4	$224.27	13.137%	$253.7323	$253.73	$253.75	$253.70
Purchase #5	$194.86	5.514%	$205.6046	$205.60	$205.60	$205.60
Purchase #6	$241.46	13.419%	$273.8615	$273.86	$273.85	$273.90
Purchase #7	$193.35	6.842%	$206.579	$206.58	$206.60	$206.60
7 purchase totals =	$1,374.81		$1,493.2987	$1,493.29	$1,493.30	$1,493.30