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	$110.41	5.253%	$116.2098	$116.21	$116.20	$116.20
Purchase #2	$78.99	9.311%	$86.3448	$86.34	$86.35	$86.30
Purchase #3	$67.27	6.349%	$71.541	$71.54	$71.55	$71.50
Purchase #4	$107.73	4.481%	$112.5574	$112.56	$112.55	$112.60
Purchase #5	$116.67	3.131%	$120.3229	$120.32	$120.30	$120.30
Purchase #6	$125.37	4.724%	$131.2925	$131.29	$131.30	$131.30
Purchase #7	$104.61	9.809%	$114.8712	$114.87	$114.85	$114.90
7 purchase totals =	$711.05		$753.1396	$753.13	$753.10	$753.10