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	$185.76	6.498%	$197.8307	$197.83	$197.85	$197.80
Purchase #2	$122.77	3.567%	$127.1492	$127.15	$127.15	$127.10
Purchase #3	$38.88	9.583%	$42.6059	$42.61	$42.60	$42.60
Purchase #4	$72.65	13.385%	$82.3742	$82.37	$82.35	$82.40
Purchase #5	$68.58	7.372%	$73.6357	$73.64	$73.65	$73.60
Purchase #6	$100.61	6.229%	$106.877	$106.88	$106.90	$106.90
Purchase #7	$157.89	10.813%	$174.9626	$174.96	$174.95	$175.00
7 purchase totals =	$747.14		$805.4353	$805.44	$805.45	$805.40