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	$175.76	5.478%	$185.3881	$185.39	$185.40	$185.40
Purchase #2	$59.54	4.224%	$62.055	$62.06	$62.05	$62.10
Purchase #3	$197.90	3.859%	$205.537	$205.54	$205.55	$205.50
Purchase #4	$109.50	5.136%	$115.1239	$115.12	$115.10	$115.10
Purchase #5	$158.44	4.675%	$165.8471	$165.85	$165.85	$165.80
Purchase #6	$94.38	12.818%	$106.4776	$106.48	$106.50	$106.50
Purchase #7	$40.55	7.729%	$43.6841	$43.68	$43.70	$43.70
7 purchase totals =	$836.07		$884.1128	$884.12	$884.15	$884.10