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	$115.67	10.165%	$127.4279	$127.43	$127.45	$127.40
Purchase #2	$188.45	7.761%	$203.0756	$203.08	$203.10	$203.10
Purchase #3	$18.91	5.813%	$20.0092	$20.01	$20.00	$20.00
Purchase #4	$21.69	5.874%	$22.9641	$22.96	$22.95	$23.00
Purchase #5	$89.71	11.594%	$100.111	$100.11	$100.10	$100.10
Purchase #6	$168.41	10.643%	$186.3339	$186.33	$186.35	$186.30
Purchase #7	$30.67	9.647%	$33.6287	$33.63	$33.65	$33.60
7 purchase totals =	$633.51		$693.5504	$693.55	$693.60	$693.50