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	$177.78	5.351%	$187.293	$187.29	$187.30	$187.30
Purchase #2	$54.26	12.635%	$61.1158	$61.12	$61.10	$61.10
Purchase #3	$100.85	7.803%	$108.7193	$108.72	$108.70	$108.70
Purchase #4	$73.43	13.163%	$83.0956	$83.10	$83.10	$83.10
Purchase #5	$54.87	12.200%	$61.5641	$61.56	$61.55	$61.60
Purchase #6	$243.98	9.498%	$267.1532	$267.15	$267.15	$267.20
Purchase #7	$234.49	3.425%	$242.5213	$242.52	$242.50	$242.50
7 purchase totals =	$939.66		$1,011.4623	$1,011.46	$1,011.40	$1,011.50