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	$83.63	13.796%	$95.1676	$95.17	$95.15	$95.20
Purchase #2	$174.46	12.819%	$196.824	$196.82	$196.80	$196.80
Purchase #3	$236.79	13.269%	$268.2097	$268.21	$268.20	$268.20
Purchase #4	$234.64	12.447%	$263.8456	$263.85	$263.85	$263.80
Purchase #5	$177.34	10.802%	$196.4963	$196.50	$196.50	$196.50
Purchase #6	$104.33	12.844%	$117.7301	$117.73	$117.75	$117.70
Purchase #7	$184.86	7.582%	$198.8761	$198.88	$198.90	$198.90
7 purchase totals =	$1,196.05		$1,337.1494	$1,337.16	$1,337.15	$1,337.10