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	$148.44	5.692%	$156.8892	$156.89	$156.90	$156.90
Purchase #2	$99.67	3.751%	$103.4086	$103.41	$103.40	$103.40
Purchase #3	$102.62	6.389%	$109.1764	$109.18	$109.20	$109.20
Purchase #4	$57.56	3.204%	$59.4042	$59.40	$59.40	$59.40
Purchase #5	$119.82	11.225%	$133.2698	$133.27	$133.25	$133.30
Purchase #6	$81.84	4.751%	$85.7282	$85.73	$85.75	$85.70
Purchase #7	$222.48	11.542%	$248.1586	$248.16	$248.15	$248.20
7 purchase totals =	$832.43		$896.0350	$896.04	$896.05	$896.10