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	$115.81	11.226%	$128.8108	$128.81	$128.80	$128.80
Purchase #2	$44.85	5.436%	$47.288	$47.29	$47.30	$47.30
Purchase #3	$119.36	3.581%	$123.6343	$123.63	$123.65	$123.60
Purchase #4	$26.36	6.434%	$28.056	$28.06	$28.05	$28.10
Purchase #5	$123.98	4.270%	$129.2739	$129.27	$129.25	$129.30
Purchase #6	$31.76	6.480%	$33.818	$33.82	$33.80	$33.80
Purchase #7	$127.53	7.455%	$137.0374	$137.04	$137.05	$137.00
7 purchase totals =	$589.65		$627.9184	$627.92	$627.90	$627.90