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	$127.27	4.565%	$133.0799	$133.08	$133.10	$133.10
Purchase #2	$26.25	3.465%	$27.1596	$27.16	$27.15	$27.20
Purchase #3	$87.89	9.570%	$96.3011	$96.30	$96.30	$96.30
Purchase #4	$131.49	13.503%	$149.2451	$149.25	$149.25	$149.20
Purchase #5	$79.78	13.132%	$90.2567	$90.26	$90.25	$90.30
Purchase #6	$120.63	9.203%	$131.7316	$131.73	$131.75	$131.70
Purchase #7	$98.88	10.533%	$109.295	$109.30	$109.30	$109.30
7 purchase totals =	$672.19		$737.0690	$737.08	$737.10	$737.10