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	$181.57	8.327%	$196.6893	$196.69	$196.70	$196.70
Purchase #2	$70.48	12.673%	$79.4119	$79.41	$79.40	$79.40
Purchase #3	$6.74	8.607%	$7.3201	$7.32	$7.30	$7.30
Purchase #4	$27.80	12.248%	$31.2049	$31.20	$31.20	$31.20
Purchase #5	$138.61	10.234%	$152.7953	$152.80	$152.80	$152.80
Purchase #6	$71.47	10.317%	$78.8436	$78.84	$78.85	$78.80
Purchase #7	$129.34	10.872%	$143.4018	$143.40	$143.40	$143.40
7 purchase totals =	$626.01		$689.6669	$689.66	$689.65	$689.60