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	$145.29	4.791%	$152.2508	$152.25	$152.25	$152.30
Purchase #2	$25.42	5.758%	$26.8837	$26.88	$26.90	$26.90
Purchase #3	$72.88	11.359%	$81.1584	$81.16	$81.15	$81.20
Purchase #4	$158.82	12.323%	$178.3914	$178.39	$178.40	$178.40
Purchase #5	$181.78	12.476%	$204.4589	$204.46	$204.45	$204.50
Purchase #6	$75.47	4.381%	$78.7763	$78.78	$78.80	$78.80
Purchase #7	$165.80	9.415%	$181.4101	$181.41	$181.40	$181.40
7 purchase totals =	$825.46		$903.3296	$903.33	$903.35	$903.50