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	$174.88	3.564%	$181.1127	$181.11	$181.10	$181.10
Purchase #2	$160.72	5.713%	$169.9019	$169.90	$169.90	$169.90
Purchase #3	$63.72	3.874%	$66.1885	$66.19	$66.20	$66.20
Purchase #4	$32.40	10.150%	$35.6886	$35.69	$35.70	$35.70
Purchase #5	$115.91	12.871%	$130.8288	$130.83	$130.85	$130.80
Purchase #6	$139.41	11.106%	$154.8929	$154.89	$154.90	$154.90
Purchase #7	$250.74	7.792%	$270.2777	$270.28	$270.30	$270.30
7 purchase totals =	$937.78		$1,008.8911	$1,008.89	$1,008.95	$1,008.90