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	$90.57	6.268%	$96.2469	$96.25	$96.25	$96.20
Purchase #2	$180.73	6.164%	$191.8702	$191.87	$191.85	$191.90
Purchase #3	$81.27	8.293%	$88.0097	$88.01	$88.00	$88.00
Purchase #4	$80.88	10.554%	$89.4161	$89.42	$89.40	$89.40
Purchase #5	$109.63	4.251%	$114.2904	$114.29	$114.30	$114.30
Purchase #6	$186.81	8.792%	$203.2343	$203.23	$203.25	$203.20
Purchase #7	$67.83	3.351%	$70.103	$70.10	$70.10	$70.10
7 purchase totals =	$797.72		$853.1706	$853.17	$853.15	$853.10