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	$154.44	10.834%	$171.172	$171.17	$171.15	$171.20
Purchase #2	$196.71	7.318%	$211.1052	$211.11	$211.10	$211.10
Purchase #3	$55.42	9.489%	$60.6788	$60.68	$60.70	$60.70
Purchase #4	$34.74	8.492%	$37.6901	$37.69	$37.70	$37.70
Purchase #5	$20.65	5.842%	$21.8564	$21.86	$21.85	$21.90
Purchase #6	$42.25	7.279%	$45.3254	$45.33	$45.35	$45.30
Purchase #7	$157.71	10.710%	$174.6007	$174.60	$174.60	$174.60
7 purchase totals =	$661.92		$722.4286	$722.44	$722.45	$722.50