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	$69.30	10.838%	$76.8107	$76.81	$76.80	$76.80
Purchase #2	$89.63	8.681%	$97.4108	$97.41	$97.40	$97.40
Purchase #3	$215.92	12.289%	$242.4544	$242.45	$242.45	$242.50
Purchase #4	$100.76	4.154%	$104.9456	$104.95	$104.95	$104.90
Purchase #5	$120.32	5.738%	$127.224	$127.22	$127.20	$127.20
Purchase #6	$209.36	11.640%	$233.7295	$233.73	$233.75	$233.70
Purchase #7	$239.76	10.472%	$264.8677	$264.87	$264.85	$264.90
7 purchase totals =	$1,045.05		$1,147.4427	$1,147.44	$1,147.40	$1,147.40