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	$164.56	12.757%	$185.5529	$185.55	$185.55	$185.60
Purchase #2	$106.31	3.478%	$110.0075	$110.01	$110.00	$110.00
Purchase #3	$174.68	12.481%	$196.4818	$196.48	$196.50	$196.50
Purchase #4	$19.64	12.221%	$22.0402	$22.04	$22.05	$22.00
Purchase #5	$77.35	6.646%	$82.4907	$82.49	$82.50	$82.50
Purchase #6	$235.47	3.360%	$243.3818	$243.38	$243.40	$243.40
Purchase #7	$205.47	8.320%	$222.5651	$222.57	$222.55	$222.60
7 purchase totals =	$983.48		$1,062.5200	$1,062.52	$1,062.55	$1,062.60