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	$222.53	5.812%	$235.4634	$235.46	$235.45	$235.50
Purchase #2	$245.83	7.751%	$264.8843	$264.88	$264.90	$264.90
Purchase #3	$45.29	11.121%	$50.3267	$50.33	$50.35	$50.30
Purchase #4	$179.77	10.788%	$199.1636	$199.16	$199.15	$199.20
Purchase #5	$51.31	4.293%	$53.5127	$53.51	$53.50	$53.50
Purchase #6	$43.62	8.398%	$47.2832	$47.28	$47.30	$47.30
Purchase #7	$56.87	10.399%	$62.7839	$62.78	$62.80	$62.80
7 purchase totals =	$845.22		$913.4178	$913.40	$913.45	$913.50