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	$194.39	6.841%	$207.6882	$207.69	$207.70	$207.70
Purchase #2	$137.87	10.686%	$152.6028	$152.60	$152.60	$152.60
Purchase #3	$87.31	4.650%	$91.3699	$91.37	$91.35	$91.40
Purchase #4	$209.28	6.643%	$223.1825	$223.18	$223.20	$223.20
Purchase #5	$187.33	6.695%	$199.8717	$199.87	$199.85	$199.90
Purchase #6	$80.54	10.787%	$89.2278	$89.23	$89.25	$89.20
Purchase #7	$129.48	12.243%	$145.3322	$145.33	$145.35	$145.30
7 purchase totals =	$1,026.20		$1,109.2751	$1,109.27	$1,109.30	$1,109.30