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	$101.29	5.851%	$107.2165	$107.22	$107.20	$107.20
Purchase #2	$174.71	12.372%	$196.3251	$196.33	$196.35	$196.30
Purchase #3	$183.67	4.448%	$191.8396	$191.84	$191.85	$191.80
Purchase #4	$89.48	8.144%	$96.7673	$96.77	$96.75	$96.80
Purchase #5	$94.64	11.462%	$105.4876	$105.49	$105.50	$105.50
Purchase #6	$9.51	6.839%	$10.1604	$10.16	$10.15	$10.20
Purchase #7	$58.51	11.619%	$65.3083	$65.31	$65.30	$65.30
7 purchase totals =	$711.81		$773.1048	$773.12	$773.10	$773.10