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	$148.83	3.589%	$154.1715	$154.17	$154.15	$154.20
Purchase #2	$55.33	3.298%	$57.1548	$57.15	$57.15	$57.20
Purchase #3	$99.33	3.822%	$103.1264	$103.13	$103.15	$103.10
Purchase #4	$212.33	5.108%	$223.1758	$223.18	$223.20	$223.20
Purchase #5	$102.27	12.334%	$114.884	$114.88	$114.90	$114.90
Purchase #6	$220.89	7.671%	$237.8345	$237.83	$237.85	$237.80
Purchase #7	$84.40	10.218%	$93.024	$93.02	$93.00	$93.00
7 purchase totals =	$923.38		$983.3710	$983.36	$983.40	$983.40