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	$117.72	8.336%	$127.5331	$127.53	$127.55	$127.50
Purchase #2	$147.35	11.300%	$164.0006	$164.00	$164.00	$164.00
Purchase #3	$64.58	13.187%	$73.0962	$73.10	$73.10	$73.10
Purchase #4	$165.94	5.349%	$174.8161	$174.82	$174.80	$174.80
Purchase #5	$93.44	13.114%	$105.6937	$105.69	$105.70	$105.70
Purchase #6	$190.69	9.279%	$208.3841	$208.38	$208.40	$208.40
Purchase #7	$228.92	4.769%	$239.8372	$239.84	$239.85	$239.80
7 purchase totals =	$1,008.64		$1,093.3610	$1,093.36	$1,093.40	$1,093.30