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	$159.38	9.729%	$174.8861	$174.89	$174.90	$174.90
Purchase #2	$221.31	13.310%	$250.7664	$250.77	$250.75	$250.80
Purchase #3	$76.76	13.205%	$86.8962	$86.90	$86.90	$86.90
Purchase #4	$165.51	9.473%	$181.1888	$181.19	$181.20	$181.20
Purchase #5	$229.50	8.810%	$249.719	$249.72	$249.70	$249.70
Purchase #6	$164.86	10.471%	$182.1225	$182.12	$182.10	$182.10
Purchase #7	$79.78	8.317%	$86.4153	$86.42	$86.40	$86.40
7 purchase totals =	$1,097.10		$1,211.9943	$1,212.01	$1,211.95	$1,212.00