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	$222.74	11.669%	$248.7315	$248.73	$248.75	$248.70
Purchase #2	$202.84	10.114%	$223.3552	$223.36	$223.35	$223.40
Purchase #3	$54.66	11.751%	$61.0831	$61.08	$61.10	$61.10
Purchase #4	$106.63	4.417%	$111.3398	$111.34	$111.35	$111.30
Purchase #5	$191.82	6.578%	$204.4379	$204.44	$204.45	$204.40
Purchase #6	$38.64	7.674%	$41.6052	$41.61	$41.60	$41.60
Purchase #7	$83.52	3.755%	$86.6562	$86.66	$86.65	$86.70
7 purchase totals =	$900.85		$977.2089	$977.22	$977.25	$977.20