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	$88.61	4.482%	$92.5815	$92.58	$92.60	$92.60
Purchase #2	$62.77	13.816%	$71.4423	$71.44	$71.45	$71.40
Purchase #3	$245.52	9.312%	$268.3828	$268.38	$268.40	$268.40
Purchase #4	$29.67	9.873%	$32.5993	$32.60	$32.60	$32.60
Purchase #5	$180.96	5.376%	$190.6884	$190.69	$190.70	$190.70
Purchase #6	$163.62	6.320%	$173.9608	$173.96	$173.95	$174.00
Purchase #7	$129.37	10.385%	$142.8051	$142.81	$142.80	$142.80
7 purchase totals =	$900.52		$972.4602	$972.46	$972.50	$972.50