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	$248.62	9.353%	$271.8734	$271.87	$271.85	$271.90
Purchase #2	$65.91	5.837%	$69.7572	$69.76	$69.75	$69.80
Purchase #3	$19.57	7.803%	$21.097	$21.10	$21.10	$21.10
Purchase #4	$240.46	11.752%	$268.7189	$268.72	$268.70	$268.70
Purchase #5	$160.32	7.329%	$172.0699	$172.07	$172.05	$172.10
Purchase #6	$104.41	10.549%	$115.4242	$115.42	$115.40	$115.40
Purchase #7	$85.66	4.221%	$89.2757	$89.28	$89.30	$89.30
7 purchase totals =	$924.95		$1,008.2163	$1,008.22	$1,008.15	$1,008.30