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	$101.60	13.809%	$115.6299	$115.63	$115.65	$115.60
Purchase #2	$185.30	5.834%	$196.1104	$196.11	$196.10	$196.10
Purchase #3	$139.99	6.737%	$149.4211	$149.42	$149.40	$149.40
Purchase #4	$174.85	12.606%	$196.8916	$196.89	$196.90	$196.90
Purchase #5	$52.25	8.785%	$56.8402	$56.84	$56.85	$56.80
Purchase #6	$243.91	12.844%	$275.2378	$275.24	$275.25	$275.20
Purchase #7	$176.44	5.633%	$186.3789	$186.38	$186.40	$186.40
7 purchase totals =	$1,074.34		$1,176.5099	$1,176.51	$1,176.55	$1,176.40