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	$96.30	10.658%	$106.5637	$106.56	$106.55	$106.60
Purchase #2	$149.52	12.471%	$168.1666	$168.17	$168.15	$168.20
Purchase #3	$166.30	9.271%	$181.7177	$181.72	$181.70	$181.70
Purchase #4	$151.52	13.773%	$172.3888	$172.39	$172.40	$172.40
Purchase #5	$28.89	4.618%	$30.2241	$30.22	$30.20	$30.20
Purchase #6	$124.39	3.320%	$128.5197	$128.52	$128.50	$128.50
Purchase #7	$244.86	13.397%	$277.6639	$277.66	$277.65	$277.70
7 purchase totals =	$961.78		$1,065.2445	$1,065.24	$1,065.15	$1,065.30