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	$247.53	3.374%	$255.8817	$255.88	$255.90	$255.90
Purchase #2	$7.28	6.842%	$7.7781	$7.78	$7.80	$7.80
Purchase #3	$90.92	12.489%	$102.275	$102.28	$102.30	$102.30
Purchase #4	$46.85	3.733%	$48.5989	$48.60	$48.60	$48.60
Purchase #5	$233.59	6.132%	$247.9137	$247.91	$247.90	$247.90
Purchase #6	$207.37	13.152%	$234.6433	$234.64	$234.65	$234.60
Purchase #7	$166.33	11.418%	$185.3216	$185.32	$185.30	$185.30
7 purchase totals =	$999.87		$1,082.4123	$1,082.41	$1,082.45	$1,082.40