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	$42.64	7.564%	$45.8653	$45.87	$45.85	$45.90
Purchase #2	$62.35	5.379%	$65.7038	$65.70	$65.70	$65.70
Purchase #3	$54.73	8.433%	$59.3454	$59.35	$59.35	$59.30
Purchase #4	$164.34	10.293%	$181.2555	$181.26	$181.25	$181.30
Purchase #5	$246.33	8.822%	$268.0612	$268.06	$268.05	$268.10
Purchase #6	$211.98	13.435%	$240.4595	$240.46	$240.45	$240.50
Purchase #7	$230.74	5.818%	$244.1645	$244.16	$244.15	$244.20
7 purchase totals =	$1,013.11		$1,104.8552	$1,104.86	$1,104.80	$1,105.00