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	$200.94	9.648%	$220.3267	$220.33	$220.35	$220.30
Purchase #2	$56.62	8.132%	$61.2243	$61.22	$61.20	$61.20
Purchase #3	$54.60	4.253%	$56.9221	$56.92	$56.90	$56.90
Purchase #4	$164.26	11.829%	$183.6903	$183.69	$183.70	$183.70
Purchase #5	$209.76	11.232%	$233.3202	$233.32	$233.30	$233.30
Purchase #6	$78.52	9.315%	$85.8341	$85.83	$85.85	$85.80
Purchase #7	$245.39	11.311%	$273.1461	$273.15	$273.15	$273.10
7 purchase totals =	$1,010.09		$1,114.4638	$1,114.46	$1,114.45	$1,114.30