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	$35.78	3.581%	$37.0613	$37.06	$37.05	$37.10
Purchase #2	$142.28	3.701%	$147.5458	$147.55	$147.55	$147.50
Purchase #3	$11.88	5.806%	$12.5698	$12.57	$12.55	$12.60
Purchase #4	$88.44	10.367%	$97.6086	$97.61	$97.60	$97.60
Purchase #5	$44.83	10.693%	$49.6237	$49.62	$49.60	$49.60
Purchase #6	$106.94	6.279%	$113.6548	$113.65	$113.65	$113.70
Purchase #7	$178.44	10.155%	$196.5606	$196.56	$196.55	$196.60
7 purchase totals =	$608.59		$654.6246	$654.62	$654.55	$654.70