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	$242.64	11.826%	$271.3346	$271.33	$271.35	$271.30
Purchase #2	$16.27	13.403%	$18.4507	$18.45	$18.45	$18.50
Purchase #3	$83.91	9.497%	$91.8789	$91.88	$91.90	$91.90
Purchase #4	$195.97	13.831%	$223.0746	$223.07	$223.05	$223.10
Purchase #5	$235.82	13.758%	$268.2641	$268.26	$268.25	$268.30
Purchase #6	$64.92	11.462%	$72.3611	$72.36	$72.35	$72.40
Purchase #7	$202.76	10.343%	$223.7315	$223.73	$223.75	$223.70
7 purchase totals =	$1,042.29		$1,169.0955	$1,169.08	$1,169.10	$1,169.20