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	$220.63	9.111%	$240.7316	$240.73	$240.75	$240.70
Purchase #2	$103.38	7.474%	$111.1066	$111.11	$111.10	$111.10
Purchase #3	$24.29	13.543%	$27.5796	$27.58	$27.60	$27.60
Purchase #4	$150.94	11.572%	$168.4068	$168.41	$168.40	$168.40
Purchase #5	$47.40	9.537%	$51.9205	$51.92	$51.90	$51.90
Purchase #6	$221.62	12.498%	$249.3181	$249.32	$249.30	$249.30
Purchase #7	$207.52	4.115%	$216.0594	$216.06	$216.05	$216.10
7 purchase totals =	$975.78		$1,065.1226	$1,065.13	$1,065.10	$1,065.10