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	$213.69	4.630%	$223.5838	$223.58	$223.60	$223.60
Purchase #2	$108.77	6.475%	$115.8129	$115.81	$115.80	$115.80
Purchase #3	$95.76	3.693%	$99.2964	$99.30	$99.30	$99.30
Purchase #4	$94.63	11.633%	$105.6383	$105.64	$105.65	$105.60
Purchase #5	$94.82	7.189%	$101.6366	$101.64	$101.65	$101.60
Purchase #6	$237.85	12.796%	$268.2853	$268.29	$268.30	$268.30
Purchase #7	$42.49	10.393%	$46.906	$46.91	$46.90	$46.90
7 purchase totals =	$888.01		$961.1593	$961.17	$961.20	$961.10