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	$172.43	11.249%	$191.8267	$191.83	$191.85	$191.80
Purchase #2	$213.81	9.155%	$233.3843	$233.38	$233.40	$233.40
Purchase #3	$47.68	12.253%	$53.5222	$53.52	$53.50	$53.50
Purchase #4	$218.65	11.686%	$244.2014	$244.20	$244.20	$244.20
Purchase #5	$97.46	13.320%	$110.4417	$110.44	$110.45	$110.40
Purchase #6	$90.65	6.705%	$96.7281	$96.73	$96.75	$96.70
Purchase #7	$220.65	6.830%	$235.7204	$235.72	$235.70	$235.70
7 purchase totals =	$1,061.33		$1,165.8248	$1,165.82	$1,165.85	$1,165.70