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	$54.36	10.113%	$59.8574	$59.86	$59.85	$59.90
Purchase #2	$120.29	6.708%	$128.3591	$128.36	$128.35	$128.40
Purchase #3	$209.34	9.533%	$229.2964	$229.30	$229.30	$229.30
Purchase #4	$67.48	6.602%	$71.935	$71.94	$71.95	$71.90
Purchase #5	$157.67	8.159%	$170.5343	$170.53	$170.55	$170.50
Purchase #6	$167.42	7.251%	$179.5596	$179.56	$179.55	$179.60
Purchase #7	$28.86	3.326%	$29.8199	$29.82	$29.80	$29.80
7 purchase totals =	$805.42		$869.3617	$869.37	$869.35	$869.40