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	$73.88	4.522%	$77.2209	$77.22	$77.20	$77.20
Purchase #2	$225.89	11.217%	$251.2281	$251.23	$251.25	$251.20
Purchase #3	$79.32	13.365%	$89.9211	$89.92	$89.90	$89.90
Purchase #4	$85.37	4.677%	$89.3628	$89.36	$89.35	$89.40
Purchase #5	$197.32	4.441%	$206.083	$206.08	$206.10	$206.10
Purchase #6	$22.35	11.494%	$24.9189	$24.92	$24.90	$24.90
Purchase #7	$119.30	4.428%	$124.5826	$124.58	$124.60	$124.60
7 purchase totals =	$803.43		$863.3174	$863.31	$863.30	$863.30