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	$103.25	6.682%	$110.1492	$110.15	$110.15	$110.10
Purchase #2	$67.27	9.798%	$73.8611	$73.86	$73.85	$73.90
Purchase #3	$41.92	9.342%	$45.8362	$45.84	$45.85	$45.80
Purchase #4	$94.45	13.751%	$107.4378	$107.44	$107.45	$107.40
Purchase #5	$75.60	9.644%	$82.8909	$82.89	$82.90	$82.90
Purchase #6	$98.74	5.467%	$104.1381	$104.14	$104.15	$104.10
Purchase #7	$211.27	10.372%	$233.1829	$233.18	$233.20	$233.20
7 purchase totals =	$692.50		$757.4962	$757.50	$757.55	$757.40