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	$173.56	6.447%	$184.7494	$184.75	$184.75	$184.70
Purchase #2	$29.39	5.679%	$31.0591	$31.06	$31.05	$31.10
Purchase #3	$42.41	3.103%	$43.726	$43.73	$43.75	$43.70
Purchase #4	$96.46	6.110%	$102.3537	$102.35	$102.35	$102.40
Purchase #5	$18.66	9.187%	$20.3743	$20.37	$20.35	$20.40
Purchase #6	$40.36	13.289%	$45.7234	$45.72	$45.70	$45.70
Purchase #7	$34.95	5.443%	$36.8523	$36.85	$36.85	$36.90
7 purchase totals =	$435.79		$464.8382	$464.83	$464.80	$464.90