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	$176.74	12.725%	$199.2302	$199.23	$199.25	$199.20
Purchase #2	$236.75	11.857%	$264.8214	$264.82	$264.80	$264.80
Purchase #3	$8.28	5.855%	$8.7648	$8.76	$8.75	$8.80
Purchase #4	$152.41	8.582%	$165.4898	$165.49	$165.50	$165.50
Purchase #5	$52.27	4.148%	$54.4382	$54.44	$54.45	$54.40
Purchase #6	$135.70	6.556%	$144.5965	$144.60	$144.60	$144.60
Purchase #7	$232.47	9.377%	$254.2687	$254.27	$254.25	$254.30
7 purchase totals =	$994.62		$1,091.6096	$1,091.61	$1,091.60	$1,091.60