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	$91.73	9.380%	$100.3343	$100.33	$100.35	$100.30
Purchase #2	$111.27	6.573%	$118.5838	$118.58	$118.60	$118.60
Purchase #3	$9.82	4.316%	$10.2438	$10.24	$10.25	$10.20
Purchase #4	$5.51	10.698%	$6.0995	$6.10	$6.10	$6.10
Purchase #5	$179.85	11.331%	$200.2288	$200.23	$200.25	$200.20
Purchase #6	$235.87	4.430%	$246.319	$246.32	$246.30	$246.30
Purchase #7	$48.81	7.391%	$52.4175	$52.42	$52.40	$52.40
7 purchase totals =	$682.86		$734.2267	$734.22	$734.25	$734.10