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	$178.51	3.104%	$184.051	$184.05	$184.05	$184.10
Purchase #2	$26.26	4.609%	$27.4703	$27.47	$27.45	$27.50
Purchase #3	$82.64	8.746%	$89.8677	$89.87	$89.85	$89.90
Purchase #4	$90.50	9.523%	$99.1183	$99.12	$99.10	$99.10
Purchase #5	$220.41	11.150%	$244.9857	$244.99	$245.00	$245.00
Purchase #6	$168.77	3.118%	$174.0322	$174.03	$174.05	$174.00
Purchase #7	$105.31	6.356%	$112.0035	$112.00	$112.00	$112.00
7 purchase totals =	$872.40		$931.5287	$931.53	$931.50	$931.60