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	$90.94	5.625%	$96.0554	$96.06	$96.05	$96.10
Purchase #2	$97.33	8.623%	$105.7228	$105.72	$105.70	$105.70
Purchase #3	$158.80	9.109%	$173.2651	$173.27	$173.25	$173.30
Purchase #4	$35.29	7.201%	$37.8312	$37.83	$37.85	$37.80
Purchase #5	$95.74	13.857%	$109.0067	$109.01	$109.00	$109.00
Purchase #6	$69.55	12.563%	$78.2876	$78.29	$78.30	$78.30
Purchase #7	$217.69	4.279%	$227.005	$227.01	$227.00	$227.00
7 purchase totals =	$765.34		$827.1738	$827.19	$827.15	$827.20