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	$57.27	4.347%	$59.7595	$59.76	$59.75	$59.80
Purchase #2	$65.85	9.780%	$72.2901	$72.29	$72.30	$72.30
Purchase #3	$232.60	8.783%	$253.0293	$253.03	$253.05	$253.00
Purchase #4	$27.26	4.167%	$28.3959	$28.40	$28.40	$28.40
Purchase #5	$60.45	7.608%	$65.049	$65.05	$65.05	$65.00
Purchase #6	$69.51	3.732%	$72.1041	$72.10	$72.10	$72.10
Purchase #7	$53.93	11.309%	$60.0289	$60.03	$60.05	$60.00
7 purchase totals =	$566.87		$610.6568	$610.66	$610.70	$610.60