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	$93.27	4.838%	$97.7824	$97.78	$97.80	$97.80
Purchase #2	$178.78	3.135%	$184.3848	$184.38	$184.40	$184.40
Purchase #3	$243.64	6.606%	$259.7349	$259.73	$259.75	$259.70
Purchase #4	$114.55	13.553%	$130.075	$130.08	$130.10	$130.10
Purchase #5	$85.57	13.261%	$96.9174	$96.92	$96.90	$96.90
Purchase #6	$77.49	10.201%	$85.3948	$85.39	$85.40	$85.40
Purchase #7	$83.52	8.382%	$90.5206	$90.52	$90.50	$90.50
7 purchase totals =	$876.82		$944.8099	$944.80	$944.85	$944.80