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	$96.57	3.814%	$100.2532	$100.25	$100.25	$100.30
Purchase #2	$188.89	10.674%	$209.0521	$209.05	$209.05	$209.10
Purchase #3	$51.41	10.610%	$56.8646	$56.86	$56.85	$56.90
Purchase #4	$156.37	6.822%	$167.0376	$167.04	$167.05	$167.00
Purchase #5	$142.34	9.823%	$156.3221	$156.32	$156.30	$156.30
Purchase #6	$44.31	8.199%	$47.943	$47.94	$47.95	$47.90
Purchase #7	$101.64	8.511%	$110.2906	$110.29	$110.30	$110.30
7 purchase totals =	$781.53		$847.7632	$847.75	$847.75	$847.80