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	$176.70	5.421%	$186.2789	$186.28	$186.30	$186.30
Purchase #2	$245.39	9.512%	$268.7315	$268.73	$268.75	$268.70
Purchase #3	$9.44	8.605%	$10.2523	$10.25	$10.25	$10.30
Purchase #4	$43.51	4.493%	$45.4649	$45.46	$45.45	$45.50
Purchase #5	$198.33	11.466%	$221.0705	$221.07	$221.05	$221.10
Purchase #6	$79.43	13.133%	$89.8615	$89.86	$89.85	$89.90
Purchase #7	$35.70	4.816%	$37.4193	$37.42	$37.40	$37.40
7 purchase totals =	$788.50		$859.0789	$859.07	$859.05	$859.20