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	$134.53	13.640%	$152.8799	$152.88	$152.90	$152.90
Purchase #2	$114.81	13.454%	$130.2565	$130.26	$130.25	$130.30
Purchase #3	$103.66	6.488%	$110.3855	$110.39	$110.40	$110.40
Purchase #4	$62.42	4.650%	$65.3225	$65.32	$65.30	$65.30
Purchase #5	$159.36	7.448%	$171.2291	$171.23	$171.25	$171.20
Purchase #6	$42.52	7.192%	$45.578	$45.58	$45.60	$45.60
Purchase #7	$232.49	5.136%	$244.4307	$244.43	$244.45	$244.40
7 purchase totals =	$849.79		$920.0822	$920.09	$920.15	$920.10