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	$187.90	13.269%	$212.8325	$212.83	$212.85	$212.80
Purchase #2	$239.98	10.753%	$265.785	$265.79	$265.80	$265.80
Purchase #3	$69.77	7.801%	$75.2128	$75.21	$75.20	$75.20
Purchase #4	$109.92	12.397%	$123.5468	$123.55	$123.55	$123.50
Purchase #5	$152.56	12.192%	$171.1601	$171.16	$171.15	$171.20
Purchase #6	$89.86	3.319%	$92.8425	$92.84	$92.85	$92.80
Purchase #7	$103.97	7.181%	$111.4361	$111.44	$111.45	$111.40
7 purchase totals =	$953.96		$1,052.8158	$1,052.82	$1,052.85	$1,052.70