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	$133.50	9.651%	$146.3841	$146.38	$146.40	$146.40
Purchase #2	$6.37	11.406%	$7.0966	$7.10	$7.10	$7.10
Purchase #3	$240.56	4.381%	$251.0989	$251.10	$251.10	$251.10
Purchase #4	$81.34	11.774%	$90.917	$90.92	$90.90	$90.90
Purchase #5	$136.44	8.293%	$147.755	$147.76	$147.75	$147.80
Purchase #6	$189.60	7.760%	$204.313	$204.31	$204.30	$204.30
Purchase #7	$139.28	12.669%	$156.9254	$156.93	$156.95	$156.90
7 purchase totals =	$927.09		$1,004.4900	$1,004.50	$1,004.50	$1,004.50