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	$41.29	7.122%	$44.2307	$44.23	$44.25	$44.20
Purchase #2	$47.93	13.432%	$54.368	$54.37	$54.35	$54.40
Purchase #3	$168.81	6.231%	$179.3286	$179.33	$179.35	$179.30
Purchase #4	$105.39	3.508%	$109.0871	$109.09	$109.10	$109.10
Purchase #5	$121.38	7.338%	$130.2869	$130.29	$130.30	$130.30
Purchase #6	$78.86	13.106%	$89.1954	$89.20	$89.20	$89.20
Purchase #7	$114.88	7.333%	$123.3042	$123.30	$123.30	$123.30
7 purchase totals =	$678.54		$729.8009	$729.81	$729.85	$729.80