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	$147.40	9.224%	$160.9962	$161.00	$161.00	$161.00
Purchase #2	$180.46	5.183%	$189.8132	$189.81	$189.80	$189.80
Purchase #3	$98.44	6.801%	$105.1349	$105.13	$105.15	$105.10
Purchase #4	$51.84	5.291%	$54.5829	$54.58	$54.60	$54.60
Purchase #5	$247.77	4.502%	$258.9246	$258.92	$258.90	$258.90
Purchase #6	$42.30	3.192%	$43.6502	$43.65	$43.65	$43.70
Purchase #7	$183.58	7.193%	$196.7849	$196.78	$196.80	$196.80
7 purchase totals =	$951.79		$1,009.8869	$1,009.87	$1,009.90	$1,009.90