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	$110.49	5.200%	$116.2355	$116.24	$116.25	$116.20
Purchase #2	$243.44	8.758%	$264.7605	$264.76	$264.75	$264.80
Purchase #3	$97.82	12.476%	$110.024	$110.02	$110.00	$110.00
Purchase #4	$156.37	10.407%	$172.6434	$172.64	$172.65	$172.60
Purchase #5	$19.65	4.404%	$20.5154	$20.52	$20.50	$20.50
Purchase #6	$170.98	4.498%	$178.6707	$178.67	$178.65	$178.70
Purchase #7	$143.50	13.328%	$162.6257	$162.63	$162.65	$162.60
7 purchase totals =	$942.25		$1,025.4752	$1,025.48	$1,025.45	$1,025.40