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	$186.39	5.420%	$196.4923	$196.49	$196.50	$196.50
Purchase #2	$166.56	12.787%	$187.858	$187.86	$187.85	$187.90
Purchase #3	$179.49	3.178%	$185.1942	$185.19	$185.20	$185.20
Purchase #4	$134.98	12.259%	$151.5272	$151.53	$151.55	$151.50
Purchase #5	$174.63	5.506%	$184.2451	$184.25	$184.25	$184.20
Purchase #6	$145.27	10.164%	$160.0352	$160.04	$160.05	$160.00
Purchase #7	$50.30	10.702%	$55.6831	$55.68	$55.70	$55.70
7 purchase totals =	$1,037.62		$1,121.0351	$1,121.04	$1,121.10	$1,121.00