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	$91.33	3.686%	$94.6964	$94.70	$94.70	$94.70
Purchase #2	$115.80	11.760%	$129.4181	$129.42	$129.40	$129.40
Purchase #3	$236.54	9.613%	$259.2786	$259.28	$259.30	$259.30
Purchase #4	$143.44	6.386%	$152.6001	$152.60	$152.60	$152.60
Purchase #5	$162.60	12.459%	$182.8583	$182.86	$182.85	$182.90
Purchase #6	$45.88	10.849%	$50.8575	$50.86	$50.85	$50.90
Purchase #7	$203.48	9.425%	$222.658	$222.66	$222.65	$222.70
7 purchase totals =	$999.07		$1,092.3670	$1,092.38	$1,092.35	$1,092.50