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	$79.71	3.805%	$82.743	$82.74	$82.75	$82.70
Purchase #2	$184.64	12.695%	$208.08	$208.08	$208.10	$208.10
Purchase #3	$221.54	6.444%	$235.816	$235.82	$235.80	$235.80
Purchase #4	$80.48	12.726%	$90.7219	$90.72	$90.70	$90.70
Purchase #5	$57.44	13.759%	$65.3432	$65.34	$65.35	$65.30
Purchase #6	$238.79	13.258%	$270.4488	$270.45	$270.45	$270.40
Purchase #7	$103.88	4.215%	$108.2585	$108.26	$108.25	$108.30
7 purchase totals =	$966.48		$1,061.4114	$1,061.41	$1,061.40	$1,061.30