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	$153.82	13.665%	$174.8395	$174.84	$174.85	$174.80
Purchase #2	$202.85	6.272%	$215.5728	$215.57	$215.55	$215.60
Purchase #3	$126.55	11.316%	$140.8704	$140.87	$140.85	$140.90
Purchase #4	$165.80	11.809%	$185.3793	$185.38	$185.40	$185.40
Purchase #5	$41.33	9.434%	$45.2291	$45.23	$45.25	$45.20
Purchase #6	$215.81	6.482%	$229.7988	$229.80	$229.80	$229.80
Purchase #7	$45.55	3.610%	$47.1944	$47.19	$47.20	$47.20
7 purchase totals =	$951.71		$1,038.8843	$1,038.88	$1,038.90	$1,038.90