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	$236.49	4.515%	$247.1675	$247.17	$247.15	$247.20
Purchase #2	$65.84	10.756%	$72.9218	$72.92	$72.90	$72.90
Purchase #3	$160.25	5.355%	$168.8314	$168.83	$168.85	$168.80
Purchase #4	$238.56	9.110%	$260.2928	$260.29	$260.30	$260.30
Purchase #5	$104.94	4.796%	$109.9729	$109.97	$109.95	$110.00
Purchase #6	$50.60	12.471%	$56.9103	$56.91	$56.90	$56.90
Purchase #7	$159.62	12.755%	$179.9795	$179.98	$180.00	$180.00
7 purchase totals =	$1,016.30		$1,096.0762	$1,096.07	$1,096.05	$1,096.10