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	$88.28	4.631%	$92.3682	$92.37	$92.35	$92.40
Purchase #2	$50.43	12.697%	$56.8331	$56.83	$56.85	$56.80
Purchase #3	$86.31	6.215%	$91.6742	$91.67	$91.65	$91.70
Purchase #4	$69.76	6.405%	$74.2281	$74.23	$74.25	$74.20
Purchase #5	$185.99	13.661%	$211.3981	$211.40	$211.40	$211.40
Purchase #6	$59.38	3.632%	$61.5367	$61.54	$61.55	$61.50
Purchase #7	$99.51	5.596%	$105.0786	$105.08	$105.10	$105.10
7 purchase totals =	$639.66		$693.1170	$693.12	$693.15	$693.10