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	$235.42	5.412%	$248.1609	$248.16	$248.15	$248.20
Purchase #2	$65.43	10.457%	$72.272	$72.27	$72.25	$72.30
Purchase #3	$149.76	9.601%	$164.1385	$164.14	$164.15	$164.10
Purchase #4	$116.91	11.535%	$130.3956	$130.40	$130.40	$130.40
Purchase #5	$134.82	3.654%	$139.7463	$139.75	$139.75	$139.70
Purchase #6	$131.53	5.511%	$138.7786	$138.78	$138.80	$138.80
Purchase #7	$168.44	9.859%	$185.0465	$185.05	$185.05	$185.00
7 purchase totals =	$1,002.31		$1,078.5384	$1,078.55	$1,078.55	$1,078.50