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	$100.69	3.731%	$104.4467	$104.45	$104.45	$104.40
Purchase #2	$80.96	10.809%	$89.711	$89.71	$89.70	$89.70
Purchase #3	$32.91	13.144%	$37.2357	$37.24	$37.25	$37.20
Purchase #4	$180.37	3.802%	$187.2277	$187.23	$187.25	$187.20
Purchase #5	$120.81	4.598%	$126.3648	$126.36	$126.35	$126.40
Purchase #6	$235.89	4.744%	$247.0806	$247.08	$247.10	$247.10
Purchase #7	$134.46	8.321%	$145.6484	$145.65	$145.65	$145.60
7 purchase totals =	$886.09		$937.7149	$937.72	$937.75	$937.60