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	$142.61	4.558%	$149.1102	$149.11	$149.10	$149.10
Purchase #2	$127.34	11.793%	$142.3572	$142.36	$142.35	$142.40
Purchase #3	$52.44	13.340%	$59.4355	$59.44	$59.45	$59.40
Purchase #4	$236.58	13.310%	$268.0688	$268.07	$268.05	$268.10
Purchase #5	$127.29	7.151%	$136.3925	$136.39	$136.40	$136.40
Purchase #6	$82.38	3.489%	$85.2542	$85.25	$85.25	$85.30
Purchase #7	$114.77	10.414%	$126.7221	$126.72	$126.70	$126.70
7 purchase totals =	$883.41		$967.3405	$967.34	$967.30	$967.40