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	$235.87	7.747%	$254.1428	$254.14	$254.15	$254.10
Purchase #2	$99.26	10.311%	$109.4947	$109.49	$109.50	$109.50
Purchase #3	$29.90	6.288%	$31.7801	$31.78	$31.80	$31.80
Purchase #4	$81.39	10.830%	$90.2045	$90.20	$90.20	$90.20
Purchase #5	$141.56	10.640%	$156.622	$156.62	$156.60	$156.60
Purchase #6	$215.40	7.613%	$231.7984	$231.80	$231.80	$231.80
Purchase #7	$138.76	7.758%	$149.525	$149.53	$149.55	$149.50
7 purchase totals =	$942.14		$1,023.5675	$1,023.56	$1,023.60	$1,023.50