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	$59.55	5.156%	$62.6204	$62.62	$62.60	$62.60
Purchase #2	$222.85	12.422%	$250.5324	$250.53	$250.55	$250.50
Purchase #3	$70.31	13.477%	$79.7857	$79.79	$79.80	$79.80
Purchase #4	$181.65	4.212%	$189.3011	$189.30	$189.30	$189.30
Purchase #5	$39.27	7.390%	$42.1721	$42.17	$42.15	$42.20
Purchase #6	$140.98	12.279%	$158.2909	$158.29	$158.30	$158.30
Purchase #7	$209.69	3.355%	$216.7251	$216.73	$216.75	$216.70
7 purchase totals =	$924.30		$999.4277	$999.43	$999.45	$999.40