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	$41.87	13.481%	$47.5145	$47.51	$47.50	$47.50
Purchase #2	$239.76	4.473%	$250.4845	$250.48	$250.50	$250.50
Purchase #3	$169.30	10.616%	$187.2729	$187.27	$187.25	$187.30
Purchase #4	$207.35	9.736%	$227.5376	$227.54	$227.55	$227.50
Purchase #5	$72.90	13.482%	$82.7284	$82.73	$82.75	$82.70
Purchase #6	$64.84	10.384%	$71.573	$71.57	$71.55	$71.60
Purchase #7	$135.25	8.861%	$147.2345	$147.23	$147.25	$147.20
7 purchase totals =	$931.27		$1,014.3454	$1,014.33	$1,014.35	$1,014.30