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	$72.69	13.630%	$82.5976	$82.60	$82.60	$82.60
Purchase #2	$168.87	9.362%	$184.6796	$184.68	$184.70	$184.70
Purchase #3	$145.35	13.620%	$165.1467	$165.15	$165.15	$165.10
Purchase #4	$79.64	5.545%	$84.056	$84.06	$84.05	$84.10
Purchase #5	$73.31	6.455%	$78.0422	$78.04	$78.05	$78.00
Purchase #6	$54.74	11.551%	$61.063	$61.06	$61.05	$61.10
Purchase #7	$196.61	7.485%	$211.3263	$211.33	$211.35	$211.30
7 purchase totals =	$791.21		$866.9114	$866.92	$866.95	$866.90